What are the guidelines for diagnosing Chronic Kidney Disease (CKD)?

Guidelines for Diagnosis of Chronic Kidney Disease

Diagnose CKD by testing both estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (ACR), with abnormalities persisting for at least 3 months: either eGFR <60 mL/min/1.73 m² or ACR ≥30 mg/g (≥3 mg/mmol). 1, 2

Diagnostic Criteria

CKD is defined as abnormalities in kidney structure or function present for more than 3 months with health implications. 1, 3 The diagnosis requires meeting at least one of two criteria:

• Decreased eGFR: <60 mL/min/1.73 m² 1, 2
• Markers of kidney damage: Primarily albuminuria ≥30 mg/g (≥3 mg/mmol), but also includes hematuria, imaging abnormalities showing reduced kidney size or cortical thickness, or pathological findings of fibrosis and atrophy 1, 2

Initial Testing Approach

Who to Test

Screen patients with risk factors including: 1, 4, 5

• Diabetes mellitus
• Hypertension
• Age >60 years
• Family history of CKD
• Systemic illnesses affecting the kidneys
• History of acute kidney injury

Do not screen the general population without risk factors. 4

Required Tests

Test both parameters simultaneously—never rely on eGFR or ACR alone: 1, 2

1. Serum creatinine with calculated eGFR using the CKD-EPI 2009 equation 1, 6
2. Urine albumin-to-creatinine ratio (ACR) from a random spot urine sample 1, 6

Use first morning void samples when possible to minimize variability, though random samples are acceptable. 7

Confirming the Diagnosis

Never diagnose CKD based on a single abnormal test result. 1, 7 A single measurement could reflect acute kidney injury or acute kidney disease rather than chronic disease. 1

Confirmation Strategy

Repeat abnormal tests to confirm persistence of abnormalities: 1, 7

Following initial detection of elevated ACR, hematuria, or low eGFR, repeat testing is mandatory before establishing a CKD diagnosis. 1

Establishing Chronicity (≥3 months duration)

Prove chronicity through any of these methods: 1

• Review past measurements of eGFR showing persistent abnormality
• Review past measurements of albuminuria, proteinuria, or urine microscopy
• Imaging findings: reduced kidney size, decreased cortical thickness
• Kidney biopsy showing fibrosis or atrophy
• Medical history of conditions known to cause CKD (diabetes, hypertension, glomerulonephritis)
• Repeat measurements within and beyond the 3-month timepoint

Clinical Pearl: You may initiate CKD-specific treatments at first presentation if CKD is highly likely based on clinical context, even before confirming 3-month chronicity. 1

Staging After Diagnosis

Once CKD is confirmed, stage using both GFR and albuminuria categories: 2

GFR Categories (G stages):

• G1: ≥90 mL/min/1.73 m² (normal/high, but kidney damage present)
• G2: 60-89 mL/min/1.73 m² (mildly decreased)
• G3a: 45-59 mL/min/1.73 m² (mildly to moderately decreased)
• G3b: 30-44 mL/min/1.73 m² (moderately to severely decreased)
• G4: 15-29 mL/min/1.73 m² (severely decreased)
• G5: <15 mL/min/1.73 m² (kidney failure) 2

Albuminuria Categories (A stages):

• A1: <30 mg/g (<3 mg/mmol) - normal to mildly increased
• A2: 30-300 mg/g (3-30 mg/mmol) - moderately increased
• A3: >300 mg/g (>30 mg/mmol) - severely increased 2

Enhanced GFR Assessment When Needed

Use creatinine-based eGFR (eGFRcr) for initial assessment in all adults at risk. 1 However, when more accurate GFR determination affects clinical decision-making, obtain cystatin C and calculate eGFR using both creatinine and cystatin C (eGFRcr-cys). 1

Situations Requiring Cystatin C Confirmation:

Use eGFRcr-cys when eGFRcr may be inaccurate: 1, 6

• Extremes of muscle mass (very high or very low)
• Extremes of body size (obesity, malnutrition)
• Severe chronic illness
• Dietary extremes (vegetarian diet, high protein intake, creatine supplements)
• Interference with creatinine assay from certain medications

For critical treatment decisions requiring maximum accuracy, measure GFR directly using plasma or urinary clearance of exogenous filtration markers (iothalamate, iohexol, DTPA, EDTA). 1

Determining the Cause

Always establish the underlying cause of CKD using: 1

• Clinical context and presenting symptoms
• Personal and family history
• Social and environmental exposures
• Complete medication review (prescription, over-the-counter, herbal)
• Physical examination findings
• Laboratory testing beyond basic eGFR/ACR
• Kidney imaging (ultrasound for size, echogenicity, obstruction)
• Genetic testing when hereditary disease suspected
• Kidney biopsy when diagnosis remains unclear and would change management 1

Kidney biopsy is safe and acceptable for evaluating cause and guiding treatment when clinically appropriate. 1

Critical Pitfalls to Avoid

• Never diagnose CKD from a single abnormal eGFR or ACR value—this could represent acute kidney injury or laboratory error 1, 7
• Avoid testing during urinary tract infection—this causes false-positive proteinuria 7
• Do not use serum creatinine alone—it misses early CKD and is affected by muscle mass, age, sex, and diet 1, 6, 5
• Do not assume chronicity without evidence—document persistence over ≥3 months or use clinical/imaging markers of chronicity 1
• Ensure laboratory uses enzymatic creatinine assays, not Jaffe method—Jaffe assays have drug and substance interference 1, 8

Monitoring Frequency After Diagnosis

Test eGFR and ACR at least annually in all patients with confirmed CKD. 7 Patients with diabetes require more frequent monitoring due to higher risk of progression. 7